The third tab within the Dialer 2.0 window is the Settings Tab.
There are two important Audio Settings:
Ringing Device - the system to ring when the call happens.
Output Device - the microphone and audio that you'd like to use for the call.
These are separate settings for a useful reason: You may want the ringing set in a way that you can never miss it, but you want to use different audio/microphone for the actual call. For example: You may want smrtPhone to ring on your computer speakers so you always hear it, but you might want to take the call on a headset.